Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

Area of Science:

• * Physics and Astronomy
• * Cosmology
• * Gravitational Wave Astronomy

Background:

• * Advanced LIGO and Virgo detectors have enabled new tests of general relativity.
• * Gravitational waves can have different polarizations beyond the two predicted by general relativity.
• * The stochastic gravitational wave background encodes information about these polarizations.

Purpose of the Study:

• * To search for a stochastic background of generically polarized gravitational waves.
• * To place direct bounds on the contributions of vector and scalar polarizations to this background.

Main Methods:

• * Analysis of data from the first observing run of Advanced LIGO.
• * Search for a stochastic gravitational wave background across multiple polarization modes.
• * Application of log-uniform priors to constrain energy densities of different polarizations.

Main Results:

• * No evidence for a stochastic gravitational wave background of any polarization was detected.
• * The first direct upper limits were placed on the energy densities of vector and scalar polarizations.
• * Specific limits at 95% credibility were established for tensor, vector, and scalar modes at 25 Hz.

Conclusions:

• * The study provides crucial constraints on alternative theories of gravity beyond standard general relativity.
• * Future gravitational wave observations can further refine these bounds and probe additional polarizations.